Conventional high gain space antennas are expensive to transport into space and place in orbit because of their size, weight, and inability to collapse in three dimensions. In order to overcome these and other disadvantages of the prior art, PCT Pat. Appl. No. PCT/US16/42462, filed Jul. 15, 2016, and U.S. patent application Ser. No. 15/154,760, filed May 13, 2016, disclose a balloon reflector antenna with an inflatable balloon. The contents of each of those applications are hereby incorporated by reference.
FIG. 1 is a diagram illustrating a satellite 100 with a large balloon reflector antenna 120 as deployed (e.g., in space) according to PCT Pat. Appl. No. PCT/US16/42462 and U.S. patent application Ser. No. 15/154,760.
As shown in FIG. 1, the balloon reflector antenna 120 includes a spherical balloon 140, which includes a surface transparent to electromagnetic waves 142 and a reflective surface 144 opposite the transparent surface 142. (The balloon 140 may also include one or more dielectric support curtains 146 across a diameter of the balloon 140 to help the balloon 140 keep its spherical shape.) The balloon reflector antenna 120 includes a feed system 160, which may be one or more feedhorns, planar antennas, spherical correctors such as a quasi-optical spherical corrector or a line feed (as illustrated in FIG. 1), or any other suitable device that receives electromagnetic waves that are reflected off the reflective surface 144 or emits electromagnetic waves that are reflected off the reflective surface 144.
When the balloon reflector antenna 120 receives a signal (e.g., from the ground), the signal passes through the transparent surface 142 and encounters the reflective surface 144, which focuses the signal into the feed system 160. When the balloon reflector antenna 120 transmits a signal (e.g., to the ground), the signal is emitted by the feed system 160 and encounters the reflective surface 144, which directs the signal through the transparent surface 142. Ideally, the feed system 160 provides a high gain and an antenna beam that is easily steered through large angles without degradation.
As shown in FIG. 1, a spherical reflective surface, such as the reflective surface 144, focuses parallel rays to a line (as opposed to a parabolic reflective surface, which focuses parallel rays to a point). The simplest “corrector” for this spherical aberration is a line feed, such as a pivoting line feed as described in U.S. patent application Ser. No. 15/154,760 or a phased array line feed as described in PCT Pat. Appl. No. PCT/US16/42462.
The satellite 100 also includes a balloon reflector canister 182, a radio frequency (RF) module 184, a telecommunications module 186, a pitch reaction wheel 188, a roll reaction wheel 189, a power module 190, and solar cells 192.
In addition to providing a high gain antenna and steerable beam at a significantly reduced weight, the spherical balloon 140 overcomes disadvantages of the prior art by collapsing in three dimensions in order to be stowed for launch.
FIG. 2 is a diagram illustrating the satellite 100 with the spherical balloon 140 and the feed system 160 stowed for launch in the balloon reflector canister 182. In some embodiments, a small (e.g., 1-2 meter) spherical balloon 140 can collapse so effectively as to stow in a single 1U CubeSat unit. In another embodiment, even a large (e.g., 10 meter) spherical balloon 140 and associated RF payload can easily fit into existing rocket fairings.
Because the feed system 160 must also be stowed for launch (for example, in one or more 1U CubeSat units), there is a need for collapsible feed systems.